The present invention relates generally to internal combustion engines and engine controls, and particularly to large engines used in demanding applications, such as work vehicles, locomotives, gensets and so forth.
Many control approaches and schemes have been devised for internal combustion engines, particularly for large, powerful diesel engines and engines running on other fuels. In railway locomotives, for example, such engines serve to generate electrical power which is transmitted to wheel-axle units. The wheel-axle units include electric motors that are driven to provide the desired tractive effort to move the locomotive and any railway cars coupled to it along railways. Other applications for large, powerful engines include ships, tractors, on and off-road trucks, electrical power generators, and so-forth.
One difficulty that arises in such applications involves the need for significant power output for the engine from either a cold start or in response to changing conditions, such as increased power demand. For example, during periods of acceleration, an operator may command higher speed and/or torque from the vehicle, requiring higher power output from the engine. In the case of locomotives and other transport vehicles, when steeper grades are encountered, additional torque or tractive effort is required to maintain the speed of a vehicle or train, requiring greater power output from the engine.
Conventional engine controls may not appropriately respond to such higher power output demands. For example, because higher power is required of the engine, the engine controls will generally cause greater amounts of fuel to be injected into the engine. The fuel increase may not be immediately matched, however, by proportionate increases in air supplied to the engine. As a result, the fuel-air mixture may become too rich during the resulting transitional period, causing a significant reduction or droop in engine speed, which is only recuperated quite slowly. Such speed droops are not generally desirable. Similarly, the richer mixture supplied to the engine can exceed design limits, resulting in inefficient combustion, and the discharge of smoke or particulate from the engine exhaust. Such discharges, while not necessarily problematic environmentally, are generally to be avoided.
There is a need, therefore, for improved engine arrangements and engine controls that can respond more quickly to start-up and power demand situations and avoid these drawbacks.